Laterally rigid primacord column



Nov. 20, 1962 N. J. SMITH 3,064,570

LATERALLY RIGID PRIMACORD COLUMN Filed DSC. 51, 1959 ifi'ja f: Y af INVENTOR NEAL J. SMITH Unite-d tates 3,064,576 Patented Nov. 2o, 1962 ffice 3,064,570 LATERALLY RIGID PRIMACORD COLUMN Neal J. Smith, Houston, Tex., assignor to Califoma Re.- search Corporation, San Francisco, Calif., a corporation of Delaware Filed Dec. 31, 1959. Ser. No. 863,184 4 Claims. (Cl. 102-20) This invention relates in general to geophysical surveying by the seismic wave reflection method and is directed more particularly to improved methods for generating artificial seismic waves for such surveying.

In Patent No. 2,755,878, issued July 24, 1956, for Method of Creating Seismic Disturbances, I have disclosed a seismic source constituting a length of linear explosive material Wound in the form of an helix with the pitch of the helix adjusted to produce a desired vertical component of a detonation velocity. In that patent, a method is disclosed for creating a seismic disturbance within an earth formation to provide for the maximum transfer of energy from the seismic disturbance into the earth formation by matching the vertical detonation velocity of an explosive medium with the propagation velocity of the surrounding earth formation. To eifect the velocity matching, a prescribed length of primacord is wound into a helical form and positioned into a shot hole as by being pulled from a cannister dropped to the bottom of the shot hole.

The present invention. is an improvement on the apparatus shown in the above-identified patent and has as its object the provision of a laterally rigid primacord column that may be positioned within a shot hole to be expanded in a predetermined pattern for matching the vertical component of detonation of the explosive of the primacord to the velocity of propagation of seismic energy within the surrounding medium.

A further object of the present invention is an improved support for a linear explosive material.

A further object of the present invention is a support for a linear explosive material that may be readily adjusted to predetermined elongation patterns to thus control the vertical detonation velocity of a seismic explosion within a shot hole.

Further objects and features of the present invention will be readily apparent to those skilled in the art from the appended drawings illustrating the certain preferred embodiment in which:

FIGURE 1A is a sectional view through the upper portion of aA cannister enclosing the linear explosive material.

FIGURE lB is a sectional view through the lower portion of a cannister and its support member.

FIG. 2 is a partial sectional View illustrating the manner for dispensing the linear explosive material and support from the cannister;

FIG. 3 is a sectional View taken along the lines 3 3 of FIG. 2;

FIG. 4 diagrammatically illustrates the package of FIG. l with the linear explosive material expanded in the shot hole.

FIG. 1 illustrates the cannister enclosing the linear explosive material with its support positioned within a shot hole. The explosive material constitutes a coiled eX- plosive material 11 of the primacord type, which is in the form of a flexible tube containing an explosive of such type that it detonates along the length of the material 11 at a very rapid rate. The upper end of the material 11 has secured-lireto a blasting cap 12 provided with blasting control wires 13. The material 11 is disposed within a container or cannister 16 having a detachable cover 17, a resilient lower portion 18 and a base portion 19 including anchors 20 for engaging the walls of the shot hole to rigidly secure the base member 19 in the shot hole, as will be more fully explained hereinafter. The cannister 16 and its contents are suspended `from a cable 14 that may be reeled into and out of a shot hole penetrating an earth formation by suitable apparatus 15 at the earths surface.

The explosive material 11 is secured to an accordion folding, semi-rigid support member 21, preferably constructed of a material such as waterproof, pressed paperboard, and alternate leaves of the' folded support are joined by adjustable lengths of a continuous cord member 22 that maybe tied at one or both sides of the folded support member. The semi-rigid support member 21 may be a continuous strip of disc-like portions or individual portions joined to each other along circumferential edges. The continuous strip may then be folded at the joined edges to establish the accordion folding as shown in FIG.l

4. The adjustable lengths of the continuous cord member 22 are then passed through appropriate holes in the disclike portion at the folds and are tied securely to the primacord 11 and the support member 21 at each fold as shownv in FIGS. 1A and 1B. The end of the'cord 22 is secured at the top of the cannister 16 to suitable rings 23 While the individual lengths of the cord 22 may determine, in a prearranged manner, the controlled expansion of -the coiled primacord column as it is positioned within the'- shot hole. In this manner accurate matching of the vertical velocity of explosion of the primacord column may;

be had with the velocity of propagation of the formation surrounding the shot hole. This feature of the present invention is diagrammatically shown in FIG. 4. It should be understood that the semi-rigid spacing member 21 may be selected to withstand a reasonable amount of lateral force so that a single cord 22 may be provided lfor the expansion of the coiled primacord column. In the single cord column, each individually folded leaf of the spacing member 19 may spring outwardly into wedged engage;

ment with the sidewalls of the shot hole, this being accomplished by merely raising the cannister upwardly through the shot hole` after it has been lowered to a dedesired depth therein. As the cannister is raised, the anchors engage and the cord 22, because of its connection to the base portion 19 by screw 24, begins to pay out of the resilient portion 18 at the open end of the cannister. As the cord pays out, the fixed engagement of cord and spacing member individually pulls each successive leaf of the folded -support and attached explosive material coil through the bottom of the cannister assembly. The interior portion of the resilient member 18 is provided with an inner peripheral ridge 25 for successively engaging the edge of each coil of the primacord with its supporting spacing members 21. In this manner, each successive coil of the explosive material pulls its neighboring coil out of the cannister as the cord 22 limits the predetermined expansion of the entire column. As illustrated in the lower portion of FIG. 1, revolved from the upper portion, the flexible end 18 of the cannister is provided with suitable grooves 26 to accommodate the cord 22 as it is payed out through the base of the cannister. The dispensing of the primacord column is accomplished as the cannister is raised upwardly through the shot hole by the recoiling of the cable 14 onto its reel 31 by appropriate hand or motor-operated means 32.

The operation of the illustrated device and its advantages in the matching of seismic velocity explosion to seismic velocity propagation should be readily apparent from the foregoing description of the assembled elements. As illustrated in FIG. 4, the cannister is lowered to the base of the shot hole and then raised to engage the anchorages 20 with the wall of the shot hole and to dispense the primacord column 11 and its support through the resilient end 18 of the cannister. After all, or an appropriate amount, of the explosive material has been dispensed from the cannister or, after the entire cannister has been emptied, the blaster 33 at the earths surface is actuated to explode the primacord column through the exploding cap 12. The explosive charge will rapidly travel through the coiled primacord with its vertical velocity being determined by the controlled expansion of the support members 21 as determined by the preestablished length of the cord 22. In this manner, the longitudinal velocity of the explosion axially along the shot hole may be readily matched with the velocity of propagation of seismic energy through the earth formation. This controlled rate of explosion will enhance the over-all force o f the seismic explosion and increase the transfer of energy into the vearth formation.

The semi-rigid supporting and spacing members 21 provide an additional feature to the seismic energy source of the present invention. This featureinsures rigidity to the column as it is dispensed from the cannister regardless of the state of consolidation of the penetrated formation. With the supports 21 made of material` that will` withstand a reasonable amount of lateral force, it is possible to maintain the spacing of the coils of the primacord column even though the shot holes should squeeze or cave in about the positioned explosive material. As previously stated, this lateral rigidity will be provided even though a single expansion controlling cord 22 is provided for thel primacord column although the double c ord will provide greater strength to withstand the collapse of the shot hole.

While a certain preferred embodiment of the invention has been specifically disclosed, it is understood that the invention is not limited thereto as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

I claim:

1. Means, for creating a seismic disturbance within a bore hole p enetrating an earth formation comprising a folded, continuous strip of substantially undeformable material, means for joining said strip together longitudinally at the folded edges thereof, said means Ifor joining including means for adjustably determining the longitudinal limiting distance individual folded sections of said continuous strip may be separated, an elongated string of explosive material, means joining said string of explosive material to said folded strip, detonating means joined to said explosive string, and means for expanding said'strip within said well bore to position said explosive string adjacent to said earth formation. 2. The apparatus of claim 1 wherein said explosive material is a predetermined length of primacord.

3. Means for creating a seismic disturbance within a well bore penetrating an earth formation comprising:

(a) a cannister,

(b) a continuous strip, accordion-folded element constituting aplurality of spacing members having lateral edges enclosable within said cannister, adjacent spacing members being joined to each other along the folded lateral edges thereof,

(c) limiting means secured to each of said spacing members along alternate joined lateral edges thereof and being operative to adjustably limit the spacing between unjoined edges of adjacent spacing members,

(d) a continuous length of explosive material supported on said spacing members,

(e) means secured to said cannister for lowering said 4. The apparatus of claim 3 wherein said means for dispensing includes means securing said limiting means to said removable portion and a flexible portion on said cannister engaging said spacing members.

References Cited in the file of this patent UNITED STATES PATENTS smith July 2,4, 1956 Turechek Jan. 17, 1961 ATENT oFFIcE CERTIFICATE 0F CORRECHGN Patent No. 3o6457o November 20 1962 Neal J. Smith rtified that er1 tion and that th It is hereby ce equring correo or appears in corrected below.

e said Letters Column l, lines 25v 3l21 lines 27 29, 36, l2y 58 and 67, column 3 y 2 14 3l and 32 and q and column ly line ll for wprmacolrol"y each occurrence read Primacord V column 2 EAL) :est:

VEST W. SWIDER Edwin In REYNOLDS esting Officer AC ti n g Commissioner of Patents UNITED STATES PATENT oTFICE 'CERTlFlCATE @F CQECHGN ?atent No. 3,064y570 November 20 1962 Neal J. Smith lt is hereby Certified that er'Tor appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l, lines 25,1 3l, 34 and 64V column 2v lines 27xz 29, 36, 42? 58 and 67Y column 3Y lines 7U l2f1 1411 3l and 329 and 36Z and column 49 line ll, for "plrimaoorolY each ocouzrrencerI read Primacord Signed and sealed this 31st day of December 1963.

IEAL) test. Edwin L REYNOLDS NEST W., SWlDER esting Officer Acting Commissioner of Patents 

